Backend Engineer

Keystone AI is a software consultancy built by engineers, for engineers. We partner with global companies to solve real, complex technical challenges. We’re deep into Applied AI and R&D, building both production-grade platforms for clients and our own open-source tools like Enthusiast (Agentic AI framework). We operate in a Forward-Deployed model. We don’t sit behind a wall of specs or wait for the tickets. We get into the trenches with the client, identify the actual challenges, and take full ownership of the solution. Our teams are small (3–9 people), autonomous, and cross-functional. What it means for you You won’t be assigned to a random project. You’ll partner directly with founders and CTOs on technical decisions, shaping systems - not just implementing them. You’ll have the autonomy to choose the right tools and the ownership to ensure the architecture performs under pressure.Your focus stays where it counts: mission-critical logic and high-impact experiments, not repetitive tasks and countless meetings. We don't do "safe or predictable". You’ll contribute to strategic open-source projects and build AI-driven solutions. Role Overview As a Backend Engineer, you’ll be integral to building and scaling platforms for our global clients. You’ll join a high-performing team where your voice matters. You’ll design and implement resilient systems while staying close to the code, bringing solutions to the table instead of just reporting problems. Responsibilities Technical Execution: Build and maintain scalable backend systems with a focus on clean, maintainable code. Proactive Problem Solving: Identify issues early and propose actionable ways to fix or optimize them. Collaboration: Work closely with the team and stakeholders to translate requirements into working technology. Knowledge Sharing: Share your findings and lessons learned from the code to help the team grow. AI Implementation: Support the integration of Applied AI features into client products. Requirements Experience: 2+ years of commercial experience in building web applications (Python or Ruby). Fundamentals: Solid understanding of OOP, clean code, and software development lifecycles. Databases: Practical knowledge of SQL and relational databases (PostgreSQL). Infrastructure: Experience with Git, Docker, and CI/CD pipelines. Mindset: Proactive, curious, and ready to take ownership of your tasks. AI-Native: You use tools like Claude or Cursor to work smarter and faster. English: Great command of written and spoken English for team and client communication. Tech Stack: Python, Ruby, PostgreSQL, AWS, Docker, Kubernetes. Value Proposition Built for the long run We hire for the company, not just a project - looking for passion driven engineers who want to grow with Keystone AI over time Small teams, real accountability. 3-9 people per engagement. We're small by design. That means your decisions carry weight and you are visible. Mission-critical work: We handle complex projects that move the needle for international brands. Our clients are scaling companies, established international brands, and large institutions. The systems you build will be under real load, with real stakes. Real Ownership: You take part in the decision making process on technology and implementation..You’re empowered to take initiative, experiment, and drive solutions that create real impact. No Micromanagement: We trust you to own your work and deliver outcomes - no unnecessary oversight. Collaborative R&D: Contribute to targeted Open-source projects and internal AI research. Growth through challenges: Complex problems and direct client exposure means you’ll grow by action. Applied AI as a first-class discipline. We don't bolt AI onto projects as an afterthought. You'll identify where it genuinely moves the needle and lead the implementation - on client work and on our own open-source tooling. The tools you want. If something makes you faster or sharper, we want you using it. Transparent progression path. We have defined engineering levels with clear criteria - you'll know exactly what each role looks like, and what it takes to get from one to the other. No ambiguity, no waiting for someone above you to move on If you didn't find all the information you were looking for, have a look at our handbook - it covers a variety of different matters that could be important at this stage. If there's anything else we did not mention that you're interested in - share your thoughts with us [email protected] Salary: Regular Engineer: 10 000 - 13 600 PLN net + VAT Regular+ Engineer: 14 800 - 19 300 PLN net + VAT Location: Office in Kraków, hybrid, fully-remote.